EFFECTS OF AGING ON THE SYSTEM
Dehydration is a common and serious problem for older adults. Normally, levels of electrolytes, acids, bases, and salts do not change as a person ages; however, in the older person, ICF levels decrease by about 8% because muscle tissue changes to adipose tissue. (Fat cells contain less water than muscle cells.) See Table 17-7.
As people age, their thirst sensation decreases; therefore, older people may become dehydrated. Many medications also cause fluid loss. Chronic diseases, such as renal failure, heart failure, or COPD, contribute to alterations in fluid and electrolyte and acid-base balance. Nutritional habits, exercise, and activity levels also influence body fluid levels.
Increased release of calcium from bones to maintain normal serum calcium levels often predisposes seniors to osteoporosis and an increased incidence of fractures from falls. Laxative use, fairly common in older people, can reduce gastrointestinal absorption of fluid and electrolytes.
Key Concept Electrolytes are vital in maintenance of homeostasis.This includes regulation of heart, muscle, and nerve function, as well as acid-base balance. Disorders related to imbalance of homeostasis include cardiac arrhythmias, diabetes, dehydration, edema, and gout. One of the most common causes of problems in homeostasis is renal failure.
NCLEX Alert During the NCLEX, be aware of the importance of aging on the body’s ability to restore or maintain homeostasis. The function of specific body organs, such as lungs and kidneys, is related to the nurse’s ability to solve clinical situations. The NCLEX may suggest ways of documenting nursing actions or client and family teaching.
TABLE 17-7. Effects of Aging on Fluid and Electrolyte Balance
|
FACTOR |
RESULT |
NURSING IMPLICATIONS |
|
Intracellular fluid levels decrease; thirst sensation declines. |
Dehydration is common. |
Encourage intake of foods and fluids; regulate temperature control. |
|
Muscle tissue turns to fat. |
Older people may gain weight. |
Encourage exercise, activity, and a balanced diet. |
|
Many medications cause fluid loss. |
Medications may contribute to dehydration. |
Be sure that the person on certain medications drinks enough water. |
|
Certain medications commonly taken by older people cause loss of electrolytes, such as potassium. |
Severe deficiency disorders may develop. |
Administer supplements as ordered. Monitor blood electrolyte levels. Observe for overt signs of electrolyte imbalances. |
|
Circulatory and renal disorders may cause fluid retention. |
Edema may develop. Inefficiency of control systems. |
Monitor the client’s sodium intake and blood pressure; encourage intake of foods with potassium; administer medications as ordered. |
KEY POINTS
• Homeostasis is a state of dynamic equilibrium, balance; the body constantly adjusts to external and internal stimuli to maintain homeostasis.
• Feedback is the relaying of information to and from organ systems (especially nervous and endocrine systems). Feedback keeps the body’s functioning capacity within normal boundaries.
• The body has two main fluid compartments: intracellular (within the cells) and extracellular. Extracellular fluid is located in blood vessels (plasma) and tissues (interstitial fluid).
• Homeostatic mechanisms involved in regulation of ECF include actions of the thirst center, antidiuretic hormone (ADH), renin-angiotensin-aldosterone system (RAA), and atrial natriuretic peptide (ANP).
• Water acts as a solvent and suspension agent. It helps regulate body temperature, pH, and fluid pressures inside and outside a cell. It assists and participates in chemical reactions.
• Electrolytes are substances that dissociate in water into ions, electrically charged particles that circulate in the body fluids and take part in the body’s chemical reactions.
• Normal saline (0.9% NaCl) is an isotonic solution. Stronger (more concentrated) solutions are hypertonic; weaker solutions are hypotonic.
• Fluids and other substances are transported into and out of cells passively (without ATP energy) or actively (with ATP energy).
• A person’s intake and output must be balanced to avoid a fluid deficit (dehydration) or a fluid excess (edema).
• The body has buffer systems that help to maintain the serum pH in the narrow range between approximately
7.35 and 7.45 (actually 7.37 and 7.43). Acids and bases are important components of this system.
• The lungs maintain or excrete carbon dioxide and the kidneys maintain or excrete bicarbonate, as part of the buffer system used to regulate pH. Arterial blood gases indicate how well the body’s acid-base balance is functioning.
• Minute fluid and electrolyte and acid-base changes occur constantly throughout the body, but the overall status in the healthy person is stability and equilibrium. To be healthy, a person’s body must maintain this balance within very close tolerances (with only minute deviation).
• The three major regulatory systems of body pH are chemical (buffer systems), biologic (blood and cellular activities), and physiologic (lungs and kidneys).
